The amino acid and carbohydrate composition of the acidic fraction IV hemorrhagin from timber rattlesnake venom will be determined. Its action on melittin and insulin will be examined. Its action on hide powder will be further investigated as to N- and C-terminals produced. The small amount of hide powder not solubilized by IV will be compared to the starting material. The purified hemorrhagin will be further compared to known collagenases. It the basic timber rattlesnake hemorrhagin which is nonhydrolytic has in fact been purified to homongeneity. Its structural characterization will be initiated. The structural basis for the three apparent forms of the brown recluse toxin will be determined. The chemical modification of this toxin will be examined further as to the actual type and number of residues modified. The distribution of 125I-labeled toxin in mice will be examined. The systemic toxin E from timber rattlesnake will also be labeled with 125I and its binding to various tissue hemogenates evaluated. The procoagulants from copperhead and timber rattlesnake venoms will be further characterized as to their action of fibrinogen. Studies on the hemorrhagins of eastern cottonmouth venom will continue as will the studies of the three essentially nontoxic proteases from northern copperhead venom.